Silkworm. Silkworm cocoons Silkworm description

The history of breeding of this butterfly, which belongs to the family of true silkworms (Bombycidae), is associated with ancient China, a country long years keeping the secret of making amazing fabric - silk. In ancient Chinese manuscripts, the silkworm was first mentioned in 2600 BC, and when archaeological excavations In the southwest of Shanxi province, silkworm cocoons were found dating back to 2000 BC. The Chinese knew how to keep their secrets - any attempt to export butterflies, caterpillars or silkworm eggs was punishable by death.

But all secrets are revealed someday. This happened with silk production. First, a certain selfless Chinese princess in the 4th century. AD, having married the king of Little Bukhara, she brought him silkworm eggs as a gift, hiding them in her hair. About 200 years later, in 552, two monks came to the Byzantine emperor Justinian, who offered to deliver silkworm eggs from distant China for a good reward. Justinian agreed. The monks went to dangerous journey and returned the same year, bringing silkworm eggs in their hollow staves. Justinian was fully aware of the importance of his purchase and by a special decree ordered the breeding of silkworms in the eastern regions of the empire. However, sericulture soon fell into decline and only after the Arab conquests it flourished again in Asia Minor, and later throughout North Africa, in Spain.

After IV crusade(1203-1204), silkworm eggs came from Constantinople to Venice, and since then silkworms have been quite successfully bred in the Po Valley. In the XIV century. Sericulture began in the south of France. And in 1596, silkworms began to be bred for the first time in Russia - first near Moscow, in the village of Izmailovo, and over time - in the southern provinces of the empire that were more suitable for this.

However, even after Europeans learned to breed silkworms and unwind cocoons, most of the silk continued to be delivered from China. For a long time, this material was worth its weight in gold and was available exclusively to the rich. Only in the twentieth century did artificial silk somewhat replace natural silk on the market, and even then, I think, not for long - after all, the properties natural silk truly unique.
Silk fabrics are incredibly durable and last a very long time. Silk is lightweight and retains heat well. Finally, natural silk is very beautiful and can be dyed evenly.

Silkworm caterpillars hatch from eggs (greens) at a temperature of 23-25 ​​degrees Celsius. In large sericulture farms, grenades are placed in special incubators for this purpose, where the required temperature and humidity are maintained. It takes 8-10 days for the eggs to develop, after which small larvae, only about 3 mm long, are born. They are dark brown in color and covered with tufts long hair. The hatched caterpillars are transferred to a special food shelf in a well-ventilated room with a temperature of 24-25 degrees Celsius. Each bookcase consists of several shelves covered with a fine mesh.

There are fresh mulberry leaves on the shelves. The caterpillars eat them with such appetite that Pasteur compared the loud crunching sound coming from the aft shelf with “the sound of rain falling on trees during a thunderstorm.”

The caterpillars' appetite is growing by leaps and bounds. Already on the second day after hatching, they eat twice as much food as on the first day, etc. On the fifth day, the caterpillars begin molting - they stop feeding and freeze, clasping a leaf with their hind legs and raising the front part of their body high. In this position they sleep for about a day, and then the larva straightens up strongly, the old skin bursts, and the caterpillar, grown and covered with delicate new skin, crawls out of its tight clothes. Then she rests for several hours and then starts eating again. Four days later the caterpillar falls asleep again before the next molt...

During its life, the silkworm caterpillar molts 4 times, and then builds a cocoon and turns into a pupa. At 20-25 degrees Celsius, the development of the larvae is completed in about a month, at more high temperature- faster. After the fourth molt, the caterpillar already looks very impressive: its body length is about 8 cm, its thickness is about 1 cm, and its weight is 3-5 g. Its body is now almost naked and colored whitish, pearl or ivory. At the end of the body there is a blunt curved horn. The caterpillar's head is large with two pairs of jaws, of which the upper one (mandibles) is especially well developed. But the main thing that makes the silkworm so attractive to humans is a small tubercle under the lower lip, from which a sticky substance oozes, which, upon contact with air, immediately hardens and turns into a silk thread.

Here, into this tubercle, the excretory ducts of two silk-secreting glands located in the body of the caterpillar flow. Each gland is formed by a long convoluted tube, the middle part of which is expanded and turned into a reservoir in which “silk liquid” accumulates. The reservoir of each gland passes into a long thin duct, which opens with an opening on the papilla of the lower lip. When the caterpillar needs to prepare the silk, it releases a stream of liquid outward, and it hardens, turning into a pair of threads. It is very thin, only 13-14 microns in diameter, but can withstand a load of about 15 g.
Even the smallest caterpillar that has just emerged from an egg can already secrete a thin thread. Whenever the baby is in danger of falling down, she releases the silk and hangs on it, like a spider hangs on its web. But after the fourth molt, the silk-secreting glands reach a particularly large sizes- up to 2/5 of the total body volume of the larva.

Now every day the caterpillar eats less and less and finally stops eating altogether. At this time, the mulberry gland is already so filled with liquid that a long thread trails behind the larva, wherever it crawls. The caterpillar, ready for pupation, restlessly crawls along the shelf in search of a suitable place for pupation. At this time, silkworm breeders place bundles of wood twigs - cocoons - on the aft shelf along the side walls.

Having found a suitable support, the caterpillar quickly crawls onto it and immediately begins its work. Holding her abdominal legs tighter to one of the twigs, she throws her head first to the right, then back, then to the left and applies her lower lip with the “silk” papilla to various places cocoon Soon a rather dense network of silk thread forms around it. But this is not the final construction, but only its basis. Having finished with the frame, the caterpillar crawls to its center - at this time, silk threads support it in the air and serve as the place where the real cocoon will be attached. And so his curling begins. As the caterpillar releases the thread, it quickly turns its head. Each turn requires 4 cm of silk thread, and the entire cocoon takes from 800 m to 1 km, and sometimes more! A caterpillar must shake its head as many as twenty-four thousand times to spin a cocoon.

It takes about 4 days to make a cocoon. Having finished its work, the exhausted caterpillar falls asleep in its silk cradle and turns into a chrysalis there. Some caterpillars, they are called carpet makers, do not make cocoons, but, crawling back and forth, line the surface of the food shelf as if with a carpet, while their pupa remains naked. Others, lovers of joint buildings, unite in twos or even threes and fours and weave a single, very large, up to 7 cm, cocoon. But these are all deviations from the norm. And usually caterpillars weave a single cocoon, the weight of which, together with the pupa, is from 1 to 4 g.

The cocoons produced by spinner caterpillars are very diverse in shape, size, and color. Some of them are completely round, others have an oval shape with a sharp end or a constriction in the middle. The smallest cocoons do not exceed 1.5-2 cm in length, and the largest reach 5-6 cm. In color, cocoons are completely white, lemon yellow, golden, dark yellow with a reddish tint and even greenish, depending on the breed silkworm. For example, striped breed The silkworm spins cocoons that are pure white, while the striped silkworm spins beautiful golden yellow cocoons.
It is interesting that the caterpillars, from which male butterflies later emerge, are more diligent silkworms: they weave denser cocoons, which require more silk thread.

After about 20 days, a butterfly emerges from the pupa and is faced with the problem of how to get out of its silken shelter. After all, unlike a caterpillar, it does not have sharp jaws... However, the butterfly has a different adaptation. Her goiter is filled with alkaline saliva, which softens the wall of the cocoon. Then the butterfly presses its head against the weakened wall, energetically helps itself with its legs, and finally gets out. The silkworm butterfly is not particularly beautiful. The color of its plump, furry body is either white with a light cream pattern, or dark grayish-brown. Females are larger than males.

The wingspan of the silkworm is about 4.5 cm, but these butterflies cannot fly. Most likely, they lost this ability through the process of constant human selection. After all, why do we need individuals in sericulture that can fly away?
Domestic butterflies generally do not tend to bother themselves with unnecessary movements. They only move slowly on their thin legs and move their shaggy antennae. During their short (about 12 days) life, they do not even feed. After alkaline saliva is released from their mouth, softening the cocoon, it closes forever.

Male silkworms change their behavior only when they meet individuals of the opposite sex. That’s when they become animated, circling around their friend, constantly flapping their wings and actively moving their legs. During the mating season, the silkworm puts pairs of butterflies in special gauze bags. A few hours after prolonged mating, the female begins to lay eggs - approximately from 300 to 800. This process takes her 5-6 days. Silkworm eggs are small, about 1.5 mm long. In winter, the eggs are kept at a relatively low temperature, and when spring comes and the mulberry trees begin to leaf out, the eggs are gradually revived by first keeping them at a temperature of 12 degrees Celsius and then placing them in a brood incubator.

But, of course, not every caterpillar that weaves a cocoon is given the opportunity to turn into a butterfly. Most of cocoons are used to obtain raw silk. The pupae are killed with steam, and the cocoons are soaked and unwound on special machines. From 100 kg of cocoons you can get approximately 9 kg of silk thread.
Silkworm spins the most beautiful yarn, but the caterpillars of some other butterflies are also capable of creating silk thread, although coarser. Thus, fagar silk is obtained from the cocoons of the East Asian atlas (Attacus attacus), and silk is obtained from the cocoons of the Chinese oak peacock eye (genus Antheraea), which is used for the production of scallop.

The history of breeding such an insect as the silkworm is extremely interesting. The technology was developed a long time ago, in Ancient China. The first mention of this production in Chinese chronicles dates back to 2600 BC, and silkworm cocoons found by archaeologists date back to 2000 BC. e. The Chinese elevated silk production to the status of a state secret, and for many centuries it was a clear priority for the country.

Much later, in the 13th century, Italy, Spain, and other countries began to breed and produce such worms North Africa, and in the 16th century - Russia. What kind of insect is this - the silkworm?

Silkworm butterfly and its offspring

The domesticated silkworm butterfly is not found in wildlife and is bred in special factories to produce natural thread. An adult is a fairly large insect. light color, reaching 6 cm in length with a wingspan of up to 5-6 cm. By breeding various breeds of this interesting butterfly Breeders from many countries are engaged in this. After all, optimal adaptation to the characteristics of different areas is the basis for profitable production and obtaining maximum income. Many breeds of silkworm have been developed. Some produce one generation per year, others two, and there are also species that produce several broods per year.

Despite its size, the silkworm butterfly has long ago lost this ability. She lives only 12 days and during this time she does not even eat, having an undeveloped oral cavity. With the coming mating season silkworm breeders deposit pairs in separate bags. After mating, the female spends 3-4 days laying eggs in the amount of 300-800 pieces in a grain, which has an oval shape with significantly varying sizes, which are directly dependent on the breed of the insect. The breeding period of the worm also depends on the species - it could be in the same year, or maybe next year.

Caterpillar - the next stage of development

The silkworm caterpillar hatches from eggs at a temperature of 23-25 ​​°C. In factory conditions, this occurs in incubators at a certain humidity and temperature. The eggs develop within 8-10 days, then a small brown silkworm larva, up to 3 mm long, pubescent with hairs, appears from the grena. Small caterpillars are placed in special trays and transferred to a well-ventilated, warm room. These containers are a structure like a bookcase, consisting of several shelves covered with mesh and having a specific purpose - here the caterpillars eat constantly. They feed exclusively fresh leaves mulberries, and the proverb “appetite comes with eating” is absolutely accurate in determining the gluttony of caterpillars. Their need for food increases and already on the second day they eat twice as much food as on the first.

Shedding

By the fifth day of life, the larva stops, freezes and begins to wait for its first moult. She sleeps for about a day, wrapping her legs around a leaf, then, when suddenly straightened, the skin bursts, freeing the caterpillar and giving it the opportunity to rest and resume satisfying its hunger. For the next four days, she eats leaves with an enviable appetite, until the next molt comes.

Caterpillar transformations

During the entire period of development (about a month), the caterpillar molts four times. The last moult turns it into a fairly large individual of a magnificent light pearl shade: the body length reaches 8 cm, the width is up to 1 cm, and the weight is 3-5 g. It stands out on the body with two pairs of well-developed jaws, especially the upper ones, called “mandibles”. ". But the most important quality that is important for the production of silk is the presence in an adult caterpillar of a tubercle under the lip, from which a special substance oozes, which hardens when it comes into contact with air and turns into silk thread.

Silk thread formation

This tubercle ends with two silk-secreting glands, which are long tubes with a middle part transformed in the caterpillar’s ​​body into a kind of reservoir that accumulates an adhesive substance, which subsequently forms a silk thread. If necessary, the caterpillar releases a stream of liquid through a hole under the lower lip, which solidifies and turns into a thin but quite strong thread. The latter plays a big role in the life of an insect and is used, as a rule, as a safety rope, since at the slightest danger it hangs on it like a spider, without fear of falling. In an adult caterpillar, silk-secreting glands occupy 2/5 of the total body weight.

Stages of cocoon construction

Having reached adulthood after the 4th moult, the caterpillar begins to lose appetite and gradually stops eating. By this time, the silk-secreting glands are filled with liquid so that a long thread constantly trails behind the larva. This means the caterpillar is ready to pupate. She begins to look for a suitable place and finds it on the cocoon rods, timely placed by the silkworm breeders along the side walls of the aft “shelves”.

Having settled on the twig, the caterpillar begins to work intensively: it alternately turns its head, applying the tubercle with the hole for the silk-secreting gland to different places on the cocoon, thereby forming a very strong network of silk thread. It turns out to be a kind of frame for future construction. Next, the caterpillar crawls to the center of its frame, holding itself in the air by threads, and begins to spin the cocoon itself.

Cocoon and pupation

When building a cocoon, the caterpillar turns its head very quickly, releasing up to 3 cm of thread for each turn. Its length to create the entire cocoon is from 0.8 to 1.5 km, and the time spent on it takes four or more days. Having finished its work, the caterpillar falls asleep in a cocoon, turning into a pupa.

The weight of the cocoon together with the pupa does not exceed 3-4 g. Silkworm cocoons come in a wide variety of sizes (from 1 to 6 cm), shape (round, oval, with bars) and color (from snow-white to golden and purple). Experts have noticed that male silkworms are more diligent in weaving cocoons. Their pupal homes differ in the density of the thread wound and its length.

And again the butterfly

After three weeks, a butterfly emerges from the pupa and needs to get out of the cocoon. This is difficult, since it is completely devoid of the jaws that adorn the caterpillar. But wise nature solved this problem: the butterfly is equipped with a special gland that produces alkaline saliva, the use of which softens the wall of the cocoon and facilitates the release of the newly formed butterfly. This is how the silkworm completes the circle of its own transformations.

However industrial breeding The silkworm interrupts the reproduction of butterflies. The bulk of cocoons are used to obtain raw silk. After all, this is already finished product, all that remains is to unwind the cocoons on special machines, having previously killed the pupae and treated the cocoons with steam and water.

So, the silkworm, which is bred in industrial scale, will probably never lose its relevance, is an excellent example of a domesticated insect that brings in quite a lot of income.

China is an amazing country filled with myths and legends. According to one of the ancient legends, the wife of the mythical Yellow Emperor, taught her people to weave and extract silk from the silkworm. How much you can believe this legend is unknown, but to this day China is breeding this butterfly.

What does it look like

This is a fairly large butterfly with a wingspan of up to 60 mm, which has unique individual characteristics. For example, in the process of evolution and domestication, it lost its ability to feed and acquired.

After emergence, she mates, lays larvae and dies. Its ancestors ate the leaves of the mulberry tree; it was in its crown that they lived, which is why the name of this insect came about.

Lifestyle

It has been noted that males, when spinning a cocoon from a single silk thread, spend a little more vital resource and time on this. As a result, the male’s cocoon turns out to be 25% heavier than that of the female. The process of creating a silk cocoon is very labor-intensive and troublesome, releasing two strong, but at the same time thin threads from the lower lip, the caterpillar weaves its house for 18-25 days to transform into a butterfly.

An important point In the life of the silkworm, it serves to arrange a place for hammering: thin rods must be installed in it, and it is in them that the silkworm will weave its house. The size of the cocoon reaches 38 mm, it is very dense with closed edges.

Reproduction

The life cycle of an insect is simple and primitive, and over many years of work with it by humans, it has been refined into a mechanism.
After mating, the female spends 2-3 days laying eggs; she produces about 600 eggs per clutch. After the appearance of a tiny caterpillar and with proper maintenance, it will grow and develop for about 25 days until it reaches maturity. And only then will preparations begin for transformation into a butterfly.

The pupa becomes a pupa on the 10th day, and only then can silk cocoons be used to produce silk thread.

Economic importance

Today you can go to silkworm breeding factories, see and learn the entire production process, but several centuries ago for the Chinese, everything related to the production of silk from silkworms was a closely guarded secret, the disclosure of which was threatened the death penalty. But there are no secrets that cannot be revealed. The same thing happened in this case. Gradually, cunning traders revealed this secret, and it became the property of many nations. Silk production began to develop in India, Europe, Russia, and Kazakhstan.

The second country where they began to engage in this profitable business, based on the reproduction of butterfly larvae, was India. Today it occupies a leading position in the production of natural silk.

The silkworm is no longer found in the wild, and all life cycle takes place under human supervision.

Modern developments make it possible to select the silkworm to such an extent that the cocoon itself has whitest color. Cocoons of gray, green or yellow color are not suitable for producing high-quality silk, so breeders do not use them in large-scale production.

The silkworm is very interesting insect, which has been known to man since ancient times as silk source. According to some data mentioned in Chinese chronicles, the insect became known as early as 2600 BC. The process of obtaining silk was a state secret for centuries in China, and silk became one of the clear trade advantages.

Starting from the 13th century, other countries, including Spain, Italy, and North African countries, mastered the technology of silk production. In the 16th century, technology reached Russia.

Nowadays, the silkworm is actively bred in many countries, and in Korea and China it is used not only to produce silk, but also for food. The exotic dishes that are prepared from it are distinguished by their originality, and silkworm larvae are used for the needs of traditional medicine.

India and China are leaders in silk production and it is in these countries that the number of silkworms is greatest.

What does a silkworm look like?

Yours unusual name this insect has earned it thanks to the tree on which it feeds. Mulberry, a tree also called mulberry, is the only source of food for the silkworm.

Silkworm caterpillar eats a tree day and night, which can even lead to its death if the caterpillars occupy such trees on the farm. To produce silk on an industrial scale, these trees are grown specifically to feed insects.

The silkworm goes through the following life cycles:

The silkworm butterfly is a large insect, and its wingspan reaches 6 centimeters. She has white color with black spots, on the wings, in the front part of them, there are notches. Pronounced comb mustache distinguish males from females, in whom this effect is almost invisible.

The butterfly has practically lost the ability to fly and modern individuals spend their entire lives without rising into the sky. This was caused by their very long detention in unnatural living conditions. Moreover, according to available facts, insects stop eating food after turning into butterflies.

Such strange features I acquired the silkworm because it was kept at home for many centuries. This has now led to the insect cannot survive without human guardianship.

Over the years of its breeding, the silkworm has managed to degenerate into two main species: monovoltine and multivoltine. The first species lays larvae once a year, and the second - up to several times a year.

Hybrid silkworms can have many differences in characteristics such as:

• body shape;
• wing color;
• dimensions and general shape butterflies;
• dimensions of the pupa;
• color and shape of caterpillars.

The larvae or eggs of this butterfly are scientifically called grena. They have a laterally flattened oval shape, with elastic transparent film. The dimensions of one egg are so small that per gram of weight their number can reach two thousand.

Immediately after the butterfly lays its eggs, they have a light milky or yellowish color. As time passes, changes occur, leading to the appearance of a pink tint in the larvae, and then to a complete change in color to purple. If the color of the eggs does not change over time, it means the larvae have died.

Silkworm eggs have a fairly long maturation period. He puts them in summer months: in July and August, and then they hibernate until spring. The processes occurring in them at this time slow down significantly in order to survive the effects of low winter temperatures.

If the grena overwinters at temperatures not lower than +15 degrees, then there is a risk of poor development in future caterpillars, so in winter it is necessary provide for grains optimal temperature regime. Caterpillars appear before leaves have time to grow on the trees, so grena is stored in refrigeration units at temperatures from 0 to -2 degrees throughout this period.

The caterpillars of this butterfly are also called silkworms, which cannot be considered a scientific name. Externally, silkworm caterpillars look like this:

Immediately after birth, the caterpillar has a very small size and a weight not exceeding half of one milligram. Despite these sizes, everything biological processes the caterpillar's growths proceed normally, and it begins to actively develop and grow.

The caterpillar has very developed jaws, pharynx and esophagus, due to which all consumed food is absorbed very quickly and well. Each of these little caterpillars has more than 8,000 muscles, allowing them to bend into intricate poses.

In forty days, the caterpillar grows to more than thirty times its original size. During the period of growth, she sheds her skin, which for natural reasons becomes small for her. This is called molting.

During molting, the silkworm caterpillar stops eating tree leaves and finds a separate place for itself, usually under the leaves, where it tightly attaches itself to them with its legs and freezes for some period. I also call this period the caterpillar's sleep.

As time passes, the head of a renewed caterpillar begins to emerge from the old skin, and then it comes out entirely. At this time you cannot touch them. This can lead to the fact that the caterpillar simply does not have time to shed its old skin and dies. During its life, the caterpillar molts four times.

The intermediate stage in the transformation of a caterpillar into a butterfly is the cocoon. Caterpillar creates a cocoon around itself and inside it turns into a butterfly. These cocoons are of greatest interest to humans.

The moment when a butterfly should be born and leave its cocoon is very easy to determine - it begins to move literally a day before, and you can hear light tapping sounds inside. This knocking appears because at this time the already mature butterfly is trying to free itself from the skin of the caterpillar. A curious fact is that the time of birth of the silkworm butterfly is always the same - from five to six in the morning.

A special liquid, similar in consistency to glue, which is secreted by butterflies, helps them free themselves from the cocoon by splitting it.

The lifespan of a moth is limited to only twenty days, and sometimes they do not even live up to 18 days. In this case it is possible meet long-livers among them who live for 25 and even 30 days.

Due to the fact that the jaws and mouth of butterflies are not sufficiently developed, they cannot feed. The main task of the butterfly is to procreate and for its short life they manage to lay many eggs. In one clutch, a female silkworm can lay up to a thousand of them.

It is noteworthy that even if an insect loses its head, egg laying process will not be interrupted. The butterfly body has several nervous systems which allows her for a long time continue laying and live, even in the absence of such a significant part of the body as the head.

Silkworm or Silkworm

The silkworm is the name given to the silkworm caterpillar. He is from the family of true silkworms, of which there are about a hundred species. Their caterpillars weave a cocoon from silk: in it the transformation of the pupa into a butterfly occurs. Some people have so much silk in their cocoon that by skillfully unwinding it, you can get threads suitable for making fabrics. Coarse varieties of silk are obtained from the cocoons of the Chinese oak peacock eye and some other silkworms (Philosamia, Telea). However, the best silk is produced by the silkworm. This butterfly is a real pet, it is completely dependent on humans. Not like bees, which can survive just fine in the wild without people.

Where does the silkworm come from and who is its wild ancestor?

Many researchers believe that its homeland is the Western Himalayas, some regions of Persia and China. Theophylla mandarin butterfly lives there, darker in color than the silkworm, but generally similar to it, and most importantly, can interbreed with it, producing hybrid offspring. Perhaps this butterfly began to be bred in old times the Chinese, and after thousands of years of skillful selection, the silkworm was produced - in the human economy the most useful insect after the bee. Artificial silk competes successfully with natural silk these days, and yet annual world products The silk obtained from the silkworm amounts to hundreds of millions of kilograms.

When and how long ago did they start breeding silkworms? The legend says: 3400 years ago a certain Fu Gi made musical instruments with strings made of silk threads. But the real breeding of silkworms and constant use Its use of silk for textile production began later: approximately four and a half thousand years ago. As if Empress Xi Ling Chi was the initiator of this useful work (for which she was elevated to the rank of deity, and every year this significant event celebrated with ritual holidays).

At first, only empresses and women were engaged in silk production high rank They kept the secrets of this matter secret. “For more than 20 centuries, the Chinese jealously guarded the monopoly of silk and protected it with laws punishing with death or torture anyone who sought to take abroad the eggs of the wonderful silkworm or divulge the secret of breeding and unwinding cocoons” (J. Rostand).

Twenty centuries is a very long time; hardly any other secrets have been kept for so long. But sooner or later the secret ceases to be secret. This is what happened with sericulture. Whether it's true or false, ancient texts say that in the 4th century AD, a Chinese princess brought her husband, the ruler of Bukhara, a priceless marriage gift - silkworm eggs. She hid them in her elaborate hairstyle.

In the same century, sericulture began to develop in some parts of India. From here, apparently (this story is probably known to many), Christian monks carried silkworm eggs and mulberry seeds in hollow staves, the leaves of which feed the caterpillars that produce precious silk. The eggs brought by the monks to Byzantium did not die; caterpillars hatched from them and cocoons were obtained. But later, sericulture, which began here, died out and only in the 8th century flourished again in the vast territory captured by the Arabs - from Central Asia to Spain.

“Our main centers of sericulture are located in Central Asia and Transcaucasia. Their position is determined by the distribution of the host plant, which is the mulberry tree. The advancement of sericulture further north is hampered by the lack of cold-resistant mulberry varieties” (Professor F.N. Pravdin).

The leaves of this tree silkworms eaten with a loud crunch, which Pasteur compared to “the sound of rain falling on trees during a thunderstorm.” This is when there are a lot of worms and they all eat. And towards the end of their larval life they eat continuously - day and night! And in any position: squeezed by neighbors, lying on their backs, on their sides and eating and eating - in a day they eat as much greenery as they themselves weigh.

They eat and grow. A tiny caterpillar emerges from the egg, about three millimeters long. And after 30-80 days, the silkworm, which has completed its development, is already 8 centimeters long and a centimeter thick. It is whitish, pearly or ivory. On its head it has six pairs of simple eyes, tactile antennae and, most importantly, what made it so valuable in the human economy - a small tubercle under the lower lip. An adhesive substance oozes from the hole at its end, which upon contact with air immediately turns into a silk thread. Later, when he weaves a cocoon, we will see how this natural silk spinning machine works.

Silkworms, strictly speaking, only eat mulberry leaves. We tried feeding it with other plants: blackberry leaves, for example, or lettuce. He ate them, but he grew worse, and the cocoons were not of the first quality.

So, first eating the soft parts of the leaves, and then, when they mature, the veins, even the petioles, the silkworm grows quickly. In the first days, it doubles its weight every day, and during its entire larval life it increases it 6-10 thousand times: before pupation it weighs 3-5 grams - more than the smallest mammals, some shrews and bats.

Frozen and hard as glass, the worm does not die. If you warm it up, it comes to life, eats again calmly, and later weaves a cocoon. But in general he is thermophilic. The most favorable temperature for him is 20-25 degrees. Then it grows quickly: its larval life, if there is enough food, is 30-35 days. When it's colder (15 degrees) - 50 days. You can make it complete all the processes necessary for the caterpillar to grow and prepare for transformation in 14 days, if you feed it abundantly and keep it at 45 degrees.

10 days after the last, fourth molt, the worm’s appetite is no longer the same as before. Soon he stops eating altogether and begins to crawl around restlessly...